Pollution characteristics of heavy metals and the risk assessment for the surface sediments from Lake Chaohu and its main tributary rivers

Abstract

为了解巢湖湖区及主要出入湖河流沉积物中重金属的污染特征,对表层沉积物中重金属元素含量进行分析,基于地积累指数法、潜在生态风险指数法和沉积物质量基准法对沉积物污染风险进行评价,并对沉积物重金属来源进行初步分析.结果表明,河流沉积物中重金属的平均含量显著高于湖区,是湖区沉积物重金属含量的1.18~5.15倍,其中南淝河Cu、Zn、Pb、As和Hg含量较高,分别是背景值的3.53、16.98、3.98、5.84和23.11倍,西半湖Cu、Zn、Pb、Cd和Hg平均含量要高于东半湖,是全湖平均的1.04~1.45倍.地积累指数法和Håkanson潜在生态风险指数法评价结果均表明,Cd和Hg是主要的生态风险贡献因子,在所调查的表层沉积物中Cd和Hg数值分别为43.17~3870.94和29.96~924.57,已处于较大风险数值.此外,源分析结果表明,巢湖湖区及主要出入湖河流表层沉积物中Cu、Zn、Pb、Cr、Hg和As相关性显著,具有相似的来源,可能来自于工业废水与生活污水.;Shallow lakes are important freshwater resources and have the functions of flood control, transportation, agriculture, aquaculture, tourism, drinking and ecological protection. The environmental quality of shallow lakes is highly related to human health and sustainable development of social economy. Rapid urbanization and economic development have resulted, progressively, in deteriorating freshwater conditions. Lake Chaohu is the fifth largest freshwater lake in China. In order to characterize the pollution characteristics of heavy metals in surface sediments of Lake Chaohu, 33 and 7 sediment samples were collected in April 2013 from Lake Chaohu and its main tributary rivers, respectively. The contents of eight heavy metals(Cu, Zn, Pb, Cr, Cd, As, Hg and Ni) in the samples were analyzed and the risk of heavy metal contamination was evaluated using geo-accumulation index, Håkanson potential ecological risk index and sediment quality guidelines. The mechanization level of various components or elements was analyzed. The results showed that the average contents of heavy metals in surface sediments of the main tributary rivers were higher from 1.18 to 5.15 times than the contents in the whole lake surfaces. The contents of Cu, Zn, Pb, As and Hg in surface sediments of Nanfei River were even higher than those of other rivers, and were 3.53, 16.98, 3.98, 5.84 and 23.11 times greater than the background values, respectively. The average contents of Cu, Zn, Pb, Cd and Hg in the west regions were higher than those of the east regions, and also higher from 1.04 to 1.45 times than those of the whole lake. The results using the geo-accumulation index and the potential ecological risk assessment both indicated that Cd and Hg were the main contribution of the potential ecological risk elements, and they had reached the serious risk level(43.17-3870.94 and 29.96-924.57). The results of source analysis revealed that contents of Cu, Zn, Pb, Cr, Hg and As were highly positively related each other, indicating that they have the same sources which may be from industrial and domestic sewage.